A natural gas company in Great Falls, Mont., wanted to educate consumers. So it printed up 25,000 scratch-and-sniff cards to show how a gas leak would smell. Then yesterday, the company tossed some of the cards. And as they were crushed in a garbage truck, the gas smell filled the town.

Several buildings were evacuated after people reported gas leaks. The company apologized, but said that their campaign, in a sense, worked.